Pollution reduction by pulsed engine compression braking

ABSTRACT

An apparatus and method for reducing pollutants in engine exhaust through the use of pulsed engine compression braking. The apparatus includes a controller, a number of engine sensors connected to the controller, and connections from the controller to the exhaust valves. Bases on data from the engine sensors, the invention opens the exhaust valves during either the compression stroke, the exhaust stroke, or both. Hot fuel mixture or hot gases are then injected into the exhaust manifold, where they burn pollutants. Optionally, pressurized air can be injected into the exhaust manifold to assist in burning pollutants.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an apparatus and method for reducing pollutants in the exhaust from an internal combustion engine through the use of pulsed engine compression braking.

[0002] Compression release engine brakes for internal combustion engines are well known as shown, for example, in U.S. Pat. Nos. 5,410,882; 5,540,201; 5,740,771; 5,813,231; 5,894,731; and 6,148,793. The purpose of such brakes is to convert the associated engine from a power source to a power sink when braking is desired. Such power sinking may be helpful to assist the wheel brakes of a vehicle propelled by the engine, thereby prolonging the life of the wheel brakes and increasing the safety of operation of the vehicle. When engine braking is desired, the flow of fuel to the engine is cut off and the engine brake is turned on. Turning on the engine brake causes it to open at least one exhaust valve in at least one engine cylinder each time the piston in that cylinder nears top dead center of its compression stroke. This releases to the exhaust manifold of the engine the gas that was compressed in the cylinder and prevents the work done in compressing that gas from being recovered in the subsequent “power” stroke of the piston. The engine therefore dissipates the work of compressing the gas thus exhausted, and that dissipated work brakes the engine and the associated vehicle. In effect, the engine brake temporarily converts the engine to a gas compressor in order to make the engine absorb work or energy.

[0003] Other methods of achieving compression braking utilize various devices to open the exhaust valve at points in the engine cycle other than top dead center on the compression stroke. For example, U.S. Pat. No. 5,540,201 discloses opening the exhaust valve near bottom dead center on the intake stroke, allowing exhaust gases from the exhaust manifold to flow into the cylinder and thus boost the pressure in the cylinder just prior to compression. This boosting results in a pressure increase which in turn causes the engine to expend more work in compressing the gas, causing additional engine braking.

[0004] Another problem commonly associated with internal combustion engines for automobiles is that these engines emit pollutants into the atmosphere. It is well known that internal combustion engines operate with the greatest fuel efficiency and the most desirable operating characteristics when the engine has reached its optimum operating temperature. It is also well known that the typical internal combustion engine has greater undesirable emissions of unburned fuel when the engine is operating below its optimum operating temperature. A variety of methods have been used to enhance engine warm-up, among them being various exhaust restriction devices that raise engine operating temperature by increasing the backpressure within the exhaust manifold, causing the engine to work harder and thus increase its operating temperature. An example of such an apparatus is disclosed in U.S. Pat. No. 6,092,371. Placing the engine under load by increasing exhaust manifold pressure is also desirable because it raises exhaust temperature, which promotes combustion and decreases carbon build up, as disclosed in U.S. Pat. No. 6,109,027. Other U.S. Patents that disclose exhaust restrictive devices are: U.S. Pat. Nos. 6,209,324; and 6,308,517.

[0005] Another method to reduce pollution from the engine is exhaust gas re-circulation, which re-burns the mixture in the engine to clean the pollutants.

[0006] However, none of these patents has recognized that pollutants from internal combustion engines can be reduced by using pulsed engine compression braking to dump hot or ignited exhaust gases from the engine cylinders into the exhaust manifold to burn pollutants.

[0007] There is a need for an apparatus and method to reduce pollution from internal combustion engines by using compression engine braking that is pulsed in response to various engine conditions. The apparatus and method should include a combination of randomly selected compression braking on the compression stroke and compression braking on the exhaust stroke. There should be a mechanism for introducing additional air into the exhaust manifold to create a higher temperature, resulting in cleaner emissions.

SUMMARY OF THE INVENTION

[0008] Apparatus for reducing pollutants in engine exhaust through the use of pulsed engine compression braking, the engine having cylinders, a crankshaft, and an exhaust manifold and a plurality of exhaust valves connected to the exhaust manifold, the engine operating in a cycle that includes a compression stroke and an exhaust stroke, the apparatus comprising:

[0009] (a) a controller;

[0010] (b) a plurality of sensors connected to the controller, the sensors detecting a plurality of engine conditions; and

[0011] (c) connections from the controller to the exhaust valves

[0012] wherein the controller reads data from the sensors and controls the opening of the exhaust valves based on piston position

[0013] wherein hot gases from the cylinders are injected into the exhaust manifold to bum pollutants therein.

[0014] A method for reducing pollutants in engine exhaust through the use of pulsed engine compression braking, the engine having cylinders, a piston, and an exhaust manifold and a plurality of exhaust valves connected to the exhaust manifold, the engine operating in a cycle that includes a compression stroke and an exhaust stroke, the method comprising the steps of:

[0015] (a) sensing a plurality of engine conditions;

[0016] (b) opening the exhaust valves based on the sensed engine conditions, the opening of the exhaust valves causing engine compression braking;

[0017] (c) injecting hot gases from the cylinders into the exhaust manifold through the exhaust valves;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] The operating environment of the present invention is shown in U.S. Pat. No. 5,540,201, herein incorporated by reference.

[0019]FIG. 1 from U.S. Pat. No. 5,540,201 shows an internal combustion engine 30, which may be of the four-cycle, compression ignition type. The invention may also be used with a diesel engine or any engine that includes a compression stroke and an exhaust stroke.

[0020] The engine repetitively undergoes intake, compression, combustion and exhaust cycles during operation.

[0021] The engine 30 includes a block 32 within which is formed a plurality of combustion chambers or cylinders 34, each of which includes an associated piston 36 therein. Intake valves 38 and exhaust valves 40 are carried in a head 41 bolted to the block 32 and operated to control the admittance and expulsion of fuel and gases into and out of each cylinder 34. A crankshaft 42 is coupled to and rotated by the pistons 36 via connecting rods 44 and a camshaft 46 is coupled to and rotates with the crankshaft 42 in synchronism therewith. The camshaft in turn drives the intake valves 38 and exhaust valves 40 through rocker arms 54, 55.

[0022] As disclosed in U.S. Pat. No. 5,740,771, herein incorporated by reference, the typical internal combustion engine operates with a four stroke cycle known as the Otto-cycle. During the first stroke, the intake valve 38 is in the open position and the piston 36 moves from the top dead center position (shown on the left in FIG. 1 of the present application) toward the bottom of the cylinder 34 while the mixture of fuel and air enters the cylinder 34 through the intake valve 38. This stroke defines an intake stroke. The second stroke of the Otto-cycle is known as the compression stroke. During the compression stroke the piston 36 rises in the cylinder 34 with both the intake 38 and exhaust 40 valves in the closed position, compressing the mixture of fuel and air in the cylinder 34. Then, during the combustion stroke, combustion of the mixture takes place forcing the piston 36 back down toward the bottom of the cylinder 34 while the intake valve 38 and the exhaust valve 40 are in the closed position. Finally, during an exhaust stroke, the exhaust valve 40 opens and the piston 36 rises in the cylinder 34 forcing exhaust out of the cylinder 34 into the exhaust manifold 60.

[0023] The apparatus of the present invention is shown in FIG. 2 as reference numeral 110.

[0024] The apparatus 110 comprises a controller 112; a plurality of sensors 114 connected to the controller 112; and connections 116 from the controller to the exhaust valves 40.

[0025] The sensors detect a plurality of engine conditions. The controller reads data from the sensors 114 and controls the opening of the exhaust valves 40 based on the position of the piston 36.

[0026] In one embodiment, the controller opens the exhaust valves 40 when the piston reaches a position slightly before top dead center (TDC) on the compression stroke. Opening the exhaust valves at this point in the Otto Cycle results in engine compression braking, as described above. In addition, however, the fuel mixture has been heated by compression. When the exhaust valves 40 are opened, the hot fuel mixture is injected into the exhaust manifold 60. The hot fuel mixture may then ignite and burn any pollutants that are in the exhaust manifold.

[0027] In a second embodiment, the controller opens the exhaust valves 40 when the piston reaches a position slightly before TDC on the exhaust stroke. That is, unlike the normal Otto Cycle operation, the exhaust valves remain closed throughout most of the exhaust stroke. This causes heating of the exhaust gases by compression. When the exhaust valves are opened, the hot gases are injected into the exhaust manifold 60, where they may assist in burning any pollutants that are in the exhaust manifold. Also, any unburnt fuel in the cylinder 34 may ignite in the exhaust manifold and further assist in burning the pollutants.

[0028] In a third embodiment, the controller opens the exhaust valves 40 both slightly before TDC on the compression stroke and slightly before TDC on the exhaust stroke. This embodiment combines the features of the first two embodiments.

[0029] The controller uses logic and the data read from the sensors 114 to determine how much before TDC to open the exhaust valves, how frequently to open the exhaust valves, and when to open the exhaust valves on the compression stroke or on the exhaust stroke.

[0030] The sensors that the controller may use include, but are not limited to: an exhaust temperature sensor (both upstream and downstream); an engine rpm sensor; a vehicle speed sensor; an accelerator pedal position sensor; an engine coolant temperature sensor; an engine fuel temperature sensor; an engine boost pressure sensor; an engine atmospheric pressure sensor; a crankshaft position/speed/timing sensor; and a camshaft position/speed/timing sensor. Data from many of these sensors is available from the engine control module (ECM) data line with the use of a decoder. However, the information that is available from the ECM varies from manufacturer to manufacturer. Therefore, additional sensors may be necessary.

[0031] A fourth embodiment of the invention uses an air pump 118 to inject pressurized air into the exhaust manifold 60. This will cause the mixture to bum more completely, reducing the pollutants.

[0032] A flow chart of the method of the present invention is shown in FIG. 3.

[0033] In the first step 200, the controller 112 receives information on engine conditions from the sensors 114. If the piston is on the compression stroke 300, the controller 112 determines 310, from the information received from the sensors, whether it is time to open the exhaust valves. If so, the controller sends a signal via connections 116 to the exhaust valves 40 to open (step 320). The controller then performs similar processing if the piston is on the exhaust stroke (400, 410) and opens the exhaust valves if appropriate (320). If the method is to include a step of injecting pressurized air into the exhaust manifold, the controller determines (500) if it is time to do, based on the data received from the sensors 114. If so, it injects air (510).

[0034] The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention. 

What is claimed:
 1. Apparatus for reducing pollutants in engine exhaust through the use of pulsed engine compression braking, the engine having cylinders, a crankshaft, and an exhaust manifold and a plurality of exhaust valves connected to the exhaust manifold, the engine operating in a cycle that includes a compression stroke and an exhaust stroke, the apparatus comprising: (a) a controller; (b) a plurality of sensors connected to the controller, the sensors detecting a plurality of engine conditions; and (c) connections from the controller to the exhaust valves wherein the controller reads data from the sensors and controls the opening of the exhaust valves based on piston position wherein hot gases from the cylinders are injected into the exhaust manifold to burn pollutants therein.
 2. The apparatus of claim 1, wherein the controller opens the exhaust valves when the piston is at a position before top dead center on the compression stroke.
 3. The apparatus of claim 1, wherein the controller opens the exhaust valves when the piston is at a position before top dead center on the exhaust stroke.
 4. The apparatus of claim 1, wherein the controller opens the exhaust valves when the piston is at a position before top dead center on the compression stroke and at a position before top dead center on the exhaust stroke.
 5. The apparatus of claim 1, further comprising an air pump connected to the exhaust manifold, the air pump controlled by the controller and adapted to inject pressurized air into the exhaust manifold to increase the temperature of pollutants burning in the exhaust manifold.
 6. The apparatus of claim 1, wherein the sensors are selected from the group consisting of: exhaust temperature sensor, engine rpm sensor, vehicle speed sensor, accelerator pedal position sensor, engine coolant temperature sensor, engine intake manifold temperature sensor, engine fuel temperature sensor, engine boost pressure sensor, engine atmospheric pressure sensor, crankshaft position/speed/timing sensor, and camshaft position/speed/timing sensor.
 7. Apparatus for reducing pollutants in engine exhaust through the use of pulsed engine compression braking, the engine having cylinders, a piston, and an exhaust manifold and a plurality of exhaust valves connected to the exhaust manifold, the engine operating in a cycle that includes a compression stroke and an exhaust stroke, the apparatus comprising: (a) a controller; (b) a plurality of sensors connected to the controller, the sensors detecting a plurality of engine conditions; (c) connections from the controller to the exhaust valves; and (d) an air pump connected to the exhaust manifold and controlled by the controller to inject pressurized air into the exhaust manifold thereby increasing the temperature of pollutants burning in the exhaust manifold; wherein the controller reads data from the sensors and controls the opening of the exhaust valves based on piston position; wherein hot gases from the cylinders are injected into the exhaust manifold to burn pollutants therein.
 8. The apparatus of claim 7, wherein the controller opens the exhaust valves when the piston is at a position before top dead center on the compression stroke.
 9. The apparatus of claim 7, wherein the controller opens the exhaust valves when the piston is at a position before top dead center on the exhaust stroke.
 10. The apparatus of claim 7, wherein the controller opens the exhaust valves when the piston is at a position before top dead center on the compression stroke and at a position before top dead center on the exhaust stroke.
 11. A method for reducing pollutants in engine exhaust through the use of pulsed engine compression braking, the engine having cylinders, a piston, and an exhaust manifold and a plurality of exhaust valves connected to the exhaust manifold, the engine operating in a cycle that includes a compression stroke and an exhaust stroke, the method comprising the steps of: (a) sensing a plurality of engine conditions; (b) opening the exhaust valves based on the sensed engine conditions, the opening of the exhaust valves causing engine compression braking; (c) injecting hot gases from the cylinders into the exhaust manifold through the exhaust valves; and (d) using the hot gases to burn pollutants in the exhaust manifold.
 12. The method of claim 11, wherein the step of opening the exhaust valves occurs when the piston is at a position before top dead center on the compression stroke.
 13. The method of claim 11, wherein the step of opening the exhaust valves occurs when the piston is at a position before top dead center on the exhaust stroke.
 14. The method of claim 11, wherein the step of opening the exhaust valves occurs when the piston is at a position before top dead center on the compression stroke and when the piston is at a position before top dead center on the exhaust stroke.
 15. The method of claim 11, further comprising the steps of injecting pressurized air into the exhaust manifold and increasing the temperature of burning pollutants in the exhaust manifold due to the injected pressurized air.
 16. The method of claim 11, wherein the step of sensing a plurality of engine conditions includes sensing engine conditions selected from the group consisting of: exhaust temperature, engine rpm, vehicle speed, accelerator pedal position, engine coolant temperature, engine intake manifold temperature, engine fuel temperature, engine boost pressure, engine atmospheric pressure, crankshaft position/speed/timing, and camshaft position/speed/timing.
 17. A method for reducing pollutants in engine exhaust through the use of pulsed engine compression braking, the engine having cylinders, a piston, and an exhaust manifold and a plurality of exhaust valves connected to the exhaust manifold, the engine operating in a cycle that includes a compression stroke and an exhaust stroke, the method comprising the steps of: (a) sensing a plurality of engine conditions; (b) opening the exhaust valves based on the sensed engine conditions, the opening of the exhaust valves causing engine compression braking; (c) injecting hot gases from the cylinders into the exhaust manifold through the exhaust valves; (d) injecting pressurized air into the exhaust manifold; and (e) using the hot gases and pressurized air to bum pollutants in the exhaust manifold.
 18. The method of claim 17, wherein the step of opening the exhaust valves occurs when the piston is at a position before top dead center on the compression stroke.
 19. The method of claim 17, wherein the step of opening the exhaust valves occurs when the piston is at a position before top dead center on the exhaust stroke.
 20. The method of claim 17, wherein the step of opening the exhaust valves occurs when the piston is at a position before top dead center on the compression stroke and when the piston is at a position before top dead center on the exhaust stroke. 